The invention relates to a diagnostic x-ray installation comprising an x-ray generator, an x-ray tube, and an x-ray image intensifier-television chain which includes an x-ray image intensifier, an optical coupling member, a television camera tube of the vidicon type, a video amplifier, a regulating installation for the illumination level of the television camera tube, a control device for controlling the functional sequences and for generating the synchronous clock pulse frequencies, a deflecting and focusing unit, and a monitor. A diagnostic x-ray installation of this type is employed in angiography, particularly in the case of cranial examinations.
In German AS 20 10 360, a diagnostic x-ray installation of this type is described. A control arrangement, through actuation of a switch, effects a brief increase in the dose rate of the x-ray tube. Simultaneously a diaphram, designed as an iris diaphram, is altered, so that the illumination level of the television camera tube is kept constant. In the fluoroscopic operation, in the case of phases which are of particular interest, a television picture with a low proportion of quantum noise is hereby generated by pressing the switch. It proves disadvantageous that the radiation exposure of the patient is simultaneously increased. Moreover, only the ratio of the useful-to-interference signal in the radiation image is improved. However, the interfering influence of the noise sources of the television chain is maintained